Method for removing ca element in high-purity quartz sand sample and high-purity quartz sand made by the method

Abstract

This invention provides a method for removing Ca from high-purity quartz sand samples and the resulting high-purity quartz sand. The method includes the following steps: S1, primary hydrochloric acid leaching; S2, hydrofluoric acid leaching; S3, secondary hydrochloric acid leaching; S4, hydrochloric acid and hydrofluoric acid leaching. The beneficial effects of this invention are: microwave acid leaching utilizes the difference in dielectric constant between impurities and the quartz matrix to induce fine cracks within the quartz, promoting the contact reaction between impurities and the acid solution, thereby removing solid inclusions from the quartz; furthermore, this invention uses different acids for synergistic stepwise acid leaching, improving the efficiency of Ca impurity removal from the quartz and obtaining high-purity and stable high-purity quartz sand.

Description

Technical Field

[0001] This invention relates to the technical field of quartz sand purification methods, specifically to a method for removing Ca element from high-purity quartz sand samples and the resulting high-purity quartz sand. Background Technology

[0002] High-purity quartz sand is an indispensable key basic material for strategic emerging industries such as electronic information, photovoltaic energy, and aerospace. Its purity directly affects the performance and quality of downstream products.

[0003] High-purity quartz sand is required for quartz crucibles used in the preparation of photovoltaic monocrystalline silicon, but only a few deposits naturally produce quartz sand that can be purified into high-purity quartz sand. Granite-type high-purity quartz, with its large scale and high quality, is a promising raw material for high-purity quartz sand. Ca is a key impurity element limiting the application of high-purity quartz products in semiconductor manufacturing processes, requiring strict control. However, there are few reports on the deep removal of Ca from granulite-type high-purity quartz raw materials. The occurrence state of Ca is an important indicator for evaluating its purity and processing purification performance. Ca mainly exists in quartz minerals as impurities, and its content and distribution directly affect the preparation and application of high-purity quartz. Typically, Ca impurities may exist in the form of gangue mineral impurities, fluid inclusion impurities, or crystal structure impurities. In the processing of high-purity quartz, Ca often becomes a key factor affecting product quality due to the difficulty in complete separation.

[0004] Studies have shown that calcium (Ca) in quartz may exist as tiny mineral inclusions, such as in carbonate minerals associated with quartz. Furthermore, Ca can also enter the quartz lattice through isomorphous substitution, leading to lattice distortion and charge imbalance. This substitution not only increases the difficulty of Ca separation but may also introduce other impurity elements, such as sodium (Na) and potassium (K). In high-purity quartz, the occurrence state of Ca has a significant impact on its properties. Ca mainly exists as fluid inclusions or lattice impurities. These impurities not only increase the alkali metal content in quartz but may also induce lattice distortion, thereby affecting the chemical stability and high-temperature resistance of quartz.

[0005] Chinese patent application CN102126727A discloses a method for purifying vein quartz under non-acid washing conditions. The main steps of this method include crushing, calcination, magnetic separation, flotation, microwave complexation, and ultrasonic separation and cleaning techniques. While this method reduces the use of acid during purification and offers some environmental protection, the high-purity quartz sand purified by this method requires further purification before it can be used in industries such as photovoltaic crucibles.

[0006] Chinese patent application CN110398402B discloses a method for purifying quartz from rocks or sand samples with different mineral compositions. This method includes the following steps: thickness measurement and rock / mineral identification, sample crushing and sieving, rinsing of fine particles, first magnetic separation, aqua regia treatment, ultrapure water washing, second magnetic separation, flotation separation, HCl-H2SiF6 etching, sodium polytungstate heavy liquid separation, ultrasonic cleaning, polarizing microscope detection, and ICP-AES determination of Al content. While this method reduces the amount of hydrofluoric acid used, its applicability is limited to high-purity quartz sand raw materials with many impurities, and research on the removal of Ca impurities is not addressed.

[0007] Patent CN117483092A discloses a process for purifying natural powdered quartz into 4N grade high-purity fine-grained quartz sand. The invention mainly includes the following steps: sieving, magnetic separation, reverse flotation, direct flotation, calcination-water quenching, and mixed acid leaching. While this method has some effect on quartz purification, its removal effect on Ca impurities is generally poor, resulting in a significantly high Ca impurity content, which affects the application of high-purity quartz.

[0008] In summary, to solve the existing problems and enable the stable and efficient production of high-purity quartz sand of granite type, it is urgent to provide a method for removing Ca element from high-purity quartz sand samples and the resulting high-purity quartz sand. Summary of the Invention

[0009] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art. For example, one objective of this invention is to provide a method for removing Ca from high-purity quartz sand samples and the resulting high-purity quartz sand. This method removes Ca from the high-purity quartz sand sample through processes such as gradient microwave acid leaching, which solves the problem of high Ca impurity content after purification of granite-type high-purity quartz raw materials, resulting in high-purity and stable high-purity quartz sand.

[0010] To achieve the above objectives, the present invention provides a method for removing Ca element from high-purity quartz sand samples, comprising the following steps:

[0011] S1, One-time hydrochloric acid leaching

[0012] The high-purity quartz sample after preliminary purification was placed in a microwave device and subjected to the first microwave acid leaching treatment with hydrochloric acid to obtain leaching sample one; then leaching sample one was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product one.

[0013] S2, hydrofluoric acid leaching

[0014] Product 1 was placed in a microwave device and subjected to a second microwave acid leaching treatment with hydrofluoric acid to obtain leaching sample 2. Then, leaching sample 2 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 2.

[0015] S3, secondary hydrochloric acid leaching

[0016] Product 2 was placed in a microwave device and subjected to a third microwave acid leaching treatment with hydrochloric acid to obtain leaching sample 3. Then, leaching sample 3 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 3.

[0017] S4, hydrochloric acid and hydrofluoric acid acid leaching

[0018] Product 3 was placed in a microwave device and subjected to a fourth microwave acid leaching treatment using a mixed acid solution of hydrochloric acid and hydrofluoric acid to obtain leaching sample 4. Then, leaching sample 4 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain high-purity quartz product.

[0019] In a preferred embodiment of this solution, in step S1, the solid-liquid ratio of the first microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrochloric acid used in the first microwave acid leaching is 5% to 20%.

[0020] In a preferred embodiment of this solution, in step S1, the first microwave acid immersion time is 1 to 8 hours, the first microwave acid immersion temperature is 30°C to 100°C, and the microwave power used for the first microwave acid immersion is 100 to 800W.

[0021] In a preferred embodiment of this solution, in step S2, the solid-liquid ratio of the second microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrofluoric acid used in the second microwave acid leaching is 5% to 20%.

[0022] In a preferred embodiment of this solution, in step S2, the second microwave acid immersion time is 1 to 8 hours, the second microwave acid immersion temperature is 30°C to 100°C, and the microwave power of the second microwave acid immersion is 100 to 800W.

[0023] In a preferred embodiment of this solution, in step S3, the solid-liquid ratio of the third microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrochloric acid used in the third microwave acid leaching is 5% to 20%.

[0024] In a preferred embodiment of this solution, in step S3, the third microwave acid immersion time is 1 to 8 hours, the third microwave acid immersion temperature is 30°C to 100°C, and the microwave power used for the third microwave acid immersion is 100 to 800W.

[0025] In a preferred embodiment of this solution, in step S4, the solid-liquid ratio of the fourth microwave acid leaching is 1:2 to 1:6, the mass fraction of the mixed acid solution used in the fourth microwave acid leaching is 5% to 20%, and the mass ratio of hydrochloric acid to hydrofluoric acid is 9:1 to 1:9.

[0026] In a preferred embodiment of this solution, in step S4, the fourth microwave pickling time is 1 to 8 hours, the fourth microwave pickling temperature is 30°C to 100°C, and the microwave power used for the fourth microwave pickling is 100 to 800W.

[0027] The present invention also provides a high-purity quartz sand, which is prepared by the above method, and the purity of the high-purity quartz sand is greater than 99.9980%.

[0028] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0029] 1) The present invention provides a method for removing Ca element from high-purity quartz sand samples. By using microwave acid leaching, the difference in dielectric constant between impurities and the quartz matrix can be used to generate fine cracks inside the quartz, promote the contact reaction between impurities and acid, and thus remove solid inclusions in the quartz.

[0030] 2) This invention uses different acids for stepwise synergistic acid leaching, which improves the removal efficiency of Ca impurity elements in quartz and obtains high-purity and stable high-purity quartz sand. Attached Figure Description

[0031] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0032] Figure 1 The present invention illustrates the method for removing Ca from high-purity quartz sand samples and the SEM scan of the raw high-purity quartz sand produced therefrom.

[0033] Figure 2 The present invention illustrates the method for removing Ca from a high-purity quartz sand sample and the SEM scan of high-purity quartz sand produced therefrom after multi-gradient microwave acid leaching, as shown in Example 3.

[0034] Figure 3 The present invention illustrates the method for removing Ca from high-purity quartz sand samples and the process flow diagram for producing high-purity quartz sand. Detailed Implementation

[0035] In the following, the method for removing Ca from high-purity quartz sand samples and the high-purity quartz sand produced therefrom will be described in detail with reference to exemplary embodiments.

[0036] It should be noted that "first", "second", "third", "fourth", etc. are merely for the convenience of description and distinction, and should not be interpreted as indicating or implying relative importance.

[0037] It should be noted that the microwave acid leaching treatment described in this invention refers to acid leaching treatment performed in a microwave environment.

[0038] It should be noted that the high-purity quartz sample after preliminary purification mentioned in this invention refers to the purified sample obtained by processing the raw ore through conventional processes such as crushing, screening, sample preparation, magnetic separation, flotation, and acid leaching.

[0039] Exemplary embodiments

[0040] refer to Figure 3 As shown, the method for removing Ca from high-purity quartz sand samples includes the following steps:

[0041] S1, hydrochloric acid leaching

[0042] Using a pre-purified high-purity quartz sample as raw material, a microwave acid leaching test of a certain concentration was conducted in a microwave device at a certain temperature, time, and microwave power to obtain leaching sample one.

[0043] Then, the leached sample 1 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 1;

[0044] S2, hydrofluoric acid leaching

[0045] Product 1 was subjected to a microwave acid leaching test of a certain concentration in a microwave device under certain temperature, time and microwave power to obtain leaching sample 2;

[0046] Then, the leached sample 2 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 2;

[0047] S3, hydrochloric acid leaching

[0048] Product 2 was subjected to a microwave acid leaching test of a certain concentration in a microwave device under certain temperature, time and microwave power to obtain leaching sample 3;

[0049] Then, the leached sample three was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product three;

[0050] S4, hydrochloric acid and hydrofluoric acid acid leaching

[0051] Product 3 was subjected to microwave acid leaching tests at a certain temperature, time, and microwave power in a microwave device to obtain leaching sample 4 at a certain ratio and concentration.

[0052] Then, the leached sample four was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain a high-purity quartz product.

[0053] In this exemplary embodiment, during microwave heating in step S1, due to the presence of inclusions and lattice impurities within the quartz, these impurities have a significantly different dielectric constant from the quartz matrix. While the quartz matrix is ​​transparent to microwaves, the internal impurities, due to their high dielectric constant, rapidly convert electromagnetic energy into internal energy. This causes the internal impurities to heat up rapidly, thereby raising the temperature of the quartz matrix. Selective microwave heating creates a large temperature difference between the internal inclusions and the quartz matrix, leading to thermal cracking of the inclusions. The resulting micro-cracks propagate outwards with the migration and phase transformation of the lattice impurities within the quartz. The increase in cracks makes it easier for the internal impurities to be removed during acid leaching. Microwave acid leaching with hydrochloric acid can react with the Ca impurities. The reaction produces CaCl2, but hydrofluoric acid readily reacts with Ca impurities to form CaF2 precipitate, which easily clogs cracks and makes the removal of impurities difficult. Therefore, preferably, step S1 uses hydrochloric acid for microwave acid leaching. The solid-liquid ratio of the first microwave acid leaching is 1:2 to 1:6 (e.g., 1:3, 1:4, 1:5, etc.), the mass fraction of hydrochloric acid in the first microwave acid leaching is 5% to 20% (e.g., 5%, 10%, 15%, 20%, etc.), the first microwave acid leaching time is 1 to 8 hours (e.g., 2 hours, 6 hours, 7 hours, etc.), the first microwave acid leaching temperature is 30℃ to 100℃ (e.g., 40℃, 50℃, 90℃, etc.), and the microwave power of the first microwave acid leaching is 100-800W (e.g., 200W, 500W, 700W, etc.).

[0054] Preferably, in this exemplary embodiment, in step S2, after microwave acid leaching with hydrochloric acid, the generated CaCl2 diffuses outward. Due to the small size of the fissures, some CaCl2 impurity ions do not diffuse easily. Therefore, microwave acid leaching with hydrofluoric acid is used to expand the fissure channels, making it easier for impurity elements to diffuse and be removed. The solid-liquid ratio of the second microwave acid leaching is 1:2 to 1:6 (e.g., 1:3, 1:4, 1:5, etc.), and the mass fraction of hydrofluoric acid used in the second microwave acid leaching is 5% to 20% (e.g., 5%, 10%, 15%, 20%, etc.). The second microwave acid leaching time is 1 to 8 hours (e.g., 2 hours, 6 hours, 7 hours, etc.), the second microwave acid leaching temperature is 30°C to 100°C (e.g., 40°C, 50°C, 90°C, etc.), and the microwave power of the second microwave acid leaching is 100 to 800W (e.g., 200W, 500W, 700W, etc.).

[0055] Preferably, in this exemplary embodiment, in step S3, since new pits and cracks are generated and new impurity elements are exposed after microwave acid pickling with hydrofluoric acid, microwave acid pickling with hydrochloric acid is continued to remove Ca impurity elements, with conditions referring to step S1; the solid-liquid ratio of the third microwave acid pickling is 1:2 to 1:6 (e.g., 1:3, 1:4, 1:5, etc.), the mass fraction of hydrochloric acid used in the third microwave acid pickling is 5% to 20% (e.g., 5%, 10%, 15%, 20%, etc.); the third microwave acid pickling time is 1 to 8 hours (e.g., 2 hours, 6 hours, 7 hours, etc.), the third microwave acid pickling temperature is 30°C to 100°C (e.g., 40°C, 50°C, 90°C, etc.), and the microwave power used in the third microwave acid pickling is 100 to 800W (e.g., 200W, 500W, 700W, etc.).

[0056] Preferably, in this exemplary embodiment, in step S4, a mixed acid solution of hydrochloric acid and hydrofluoric acid is added for microwave acid leaching again to further remove Ca impurities; the solid-liquid ratio of the fourth microwave acid leaching is 1:2 to 1:6 (e.g., 1:3, 1:4, 1:5, etc.), the mass fraction of the mixed acid solution used in the fourth microwave acid leaching is 5% to 20% (e.g., 5%, 10%, 15%, 20%, etc.), and the mass ratio of hydrochloric acid to hydrofluoric acid is 9:1 to 1:9 (e.g., 3:1, 1:1, 1:5, 1:8, etc.); the fourth microwave acid leaching time is 1 to 8 hours (e.g., 2 hours, 6 hours, 7 hours, etc.), the fourth microwave acid leaching temperature is 30°C to 100°C (e.g., 40°C, 50°C, 90°C, etc.), and the microwave power used in the fourth microwave acid leaching is 100 to 800W (e.g., 200W, 500W, 700W, etc.).

[0057] To better understand the exemplary embodiments of the present invention described above, further explanation is provided below with reference to examples.

[0058] The analysis results of the quartz sand product obtained from the production of a certain type of high-purity quartz raw material (white granite) are shown in Table 1.

[0059] Table 1. Multi-element analysis results of purified samples

[0060]

[0061]

[0062] Example 1

[0063] The method for removing Ca from high-purity quartz sand samples includes the following steps:

[0064] S1, hydrochloric acid leaching

[0065] Using a pre-purified high-purity quartz sample as raw material, a microwave acid leaching test was conducted in a microwave device at 30℃ and 300W microwave power with a solid-liquid ratio of 1:2 and 5% hydrochloric acid (time 1h) to obtain leaching sample one.

[0066] Then, the leached sample 1 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 1;

[0067] S2, hydrofluoric acid leaching

[0068] Product 1 was subjected to a microwave acid leaching test with hydrofluoric acid at a solid-liquid ratio of 1:2.5% (time 1h) in a microwave device at 30℃ and 300W microwave power to obtain leaching sample 2.

[0069] Then, the leached sample 2 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 2;

[0070] S3, hydrochloric acid leaching

[0071] Product 2 was subjected to microwave acid leaching test with 5% hydrochloric acid at a solid-liquid ratio of 1:2 (time 1h) in a microwave device at 30℃ and 300W microwave power to obtain leaching sample 3;

[0072] Then, the leached sample three was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product three;

[0073] S4, hydrochloric acid and hydrofluoric acid acid leaching

[0074] Product 3 was subjected to microwave acid leaching test (time 1h) in a microwave device at 30℃ and 300W microwave power with a solid-liquid ratio of 1:2 and 5% mixed acid (HCl:HF = 9:1) to obtain leaching sample 4;

[0075] Then, the leached sample four was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain a high-purity quartz product.

[0076] Table 2 Example 1 Chemical Analysis Results of High-Purity Quartz Sand Sample

[0077] element Al B Ca Cu Fe K Li Mg <![CDATA[Content / 10 -6 > 10.96 0.10 1.05 0.05 0.86 0.70 0.04 0.12 element Mn Na Ni P Ti Zn Total <![CDATA[SiO2]]> <![CDATA[Content / 10 -6 > 0.02 1.45 <0.01 0.47 2.22 0.07 18.12 99.9982％

[0078] Example 2

[0079] The method for removing Ca from high-purity quartz sand samples includes the following steps:

[0080] S1, hydrochloric acid leaching

[0081] Using a pre-purified high-purity quartz sample as raw material, a microwave acid leaching test was conducted in a microwave device at 60℃, 5h time, and 500W microwave power with a solid-liquid ratio of 1:4 and 10% hydrochloric acid (5h time) to obtain leaching sample one.

[0082] Then, the leached sample 1 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 1;

[0083] S2, hydrofluoric acid leaching

[0084] Product 1 was subjected to a microwave acid leaching test with 10% hydrofluoric acid at a solid-liquid ratio of 1:4 (time 5h) in a microwave device at 60℃ and 500W microwave power to obtain leaching sample 2.

[0085] Then, the leached sample 2 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 2;

[0086] S3, hydrochloric acid leaching

[0087] Product 2 was subjected to a microwave acid leaching test with 10% hydrochloric acid at a solid-liquid ratio of 1:4 (for 5 hours) in a microwave device at 60℃ and 500W microwave power to obtain leaching sample 3.

[0088] Then, the leached sample three was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product three;

[0089] S4, hydrochloric acid and hydrofluoric acid acid leaching

[0090] Product 3 was subjected to microwave acid leaching test (5h) in a microwave device at 60℃ and 500W microwave power with a solid-liquid ratio of 1:4 and 10% mixed acid of HCl:HF = 6:4 to obtain leaching sample 4.

[0091] Then, the leached sample four was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain a high-purity quartz product.

[0092] Table 3. Chemical analysis results of Example 2 high-purity quartz sand sample.

[0093] element Al B Ca Cu Fe K Li Mg <![CDATA[Content / 10 -6 > 10.55 0.12 0.77 <0.01 0.44 0.62 0.03 0.19 element Mn Na Ni P Ti Zn Total <![CDATA[SiO2]]> <![CDATA[Content / 10 -6 > <0.01 1.35 0.02 0.35 2.02 0.05 16.53 99.9983％

[0094] Example 3

[0095] The method for removing Ca from high-purity quartz sand samples includes the following steps:

[0096] S1, hydrochloric acid leaching

[0097] Using a pre-purified high-purity quartz sample as raw material, a microwave acid leaching test was conducted in a microwave device at 100℃ and 800W microwave power with a solid-liquid ratio of 1:6 and 20% hydrochloric acid (time 8h) to obtain leaching sample one.

[0098] Then, the leached sample 1 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 1;

[0099] S2, hydrofluoric acid leaching

[0100] Product 1 was subjected to a microwave acid leaching test with 20% hydrofluoric acid at a solid-liquid ratio of 1:6 (time 8h) in a microwave device at 100℃ and 800W microwave power to obtain leaching sample 2.

[0101] Then, the leached sample 2 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 2;

[0102] S3, hydrochloric acid leaching

[0103] Product 2 was subjected to microwave acid leaching test with 20% hydrochloric acid at a solid-liquid ratio of 1:6 (time 8h) in a microwave device at 100℃ and 800W microwave power to obtain leaching sample 3;

[0104] Then, the leached sample three was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product three;

[0105] S4, hydrochloric acid and hydrofluoric acid acid leaching

[0106] Product 3 was subjected to microwave acid leaching test (8h) in a microwave device at 100℃ and 800W microwave power with a solid-liquid ratio of 1:6 and 20% mixed acid (HCl:HF = 1:9) to obtain leaching sample 4.

[0107] Then, the leached sample four was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain a high-purity quartz product.

[0108] Table 4. Chemical analysis results of Example 2 high-purity quartz sand sample.

[0109] element Al B Ca Cu Fe K Li Mg <![CDATA[Content / 10 -6 > 10.73 0.1 0.52 0.02 0.24 0.57 0.05 0.15 element Mn Na Ni P Ti Zn Total <![CDATA[SiO2]]> <![CDATA[Content / 10 -6 > <0.01 1.37 0.02 0.24 1.89 0.03 15.94 99.9984％

[0110] The inventive principle of this invention is as follows:

[0111] During microwave heating of quartz, inclusions and lattice impurities within the quartz exhibit significant differences in dielectric properties compared to the quartz matrix. Since the quartz matrix is ​​transparent to microwaves, and impurities, due to their high dielectric constant, rapidly absorb electromagnetic energy and convert it into heat, the temperature of the impurity region rises sharply and is conducted to the quartz matrix. This selective heating effect creates a significant temperature gradient between the impurities and the matrix, triggering thermal cracking of the inclusions. The resulting microcracks gradually expand as the impurities migrate within the lattice and undergo phase changes. This crack network development creates favorable conditions for the efficient removal of impurities in the subsequent acid leaching process. While microwave acid leaching with hydrochloric acid can react with Ca impurities to form CaCl2, hydrofluoric acid readily reacts with Ca impurities to form CaF2 precipitate, which easily clogs the cracks and makes impurity removal difficult. Therefore, microwave acid leaching with hydrochloric acid is used first to remove exposed Ca impurities. During the leaching process, the generated CaCl2 diffuses outwards, and because the cracks are too small, some Ca... 2+ Impurity ions do not diffuse easily. Therefore, after microwave acid leaching with hydrochloric acid, the sample is cleaned and then microwave acid leaching with hydrofluoric acid is used to expand the crack channels, making it easier for impurity elements to diffuse and be removed. At the same time, microwave acid leaching with hydrofluoric acid will create new pits, which will expose new Ca impurity elements. Therefore, microwave acid leaching with hydrochloric acid is continued to remove Ca impurity elements. Finally, a mixed acid solution of hydrochloric acid and hydrofluoric acid is added for microwave acid leaching to further reduce the content of Ca impurity elements.

[0112] Figure 1 This is a SEM scan of the raw sand sample of high-purity quartz. Figure 2 This is a SEM scan of quartz sand after multi-gradient microwave acid leaching, as shown in Example 3. Figure 1 and Figure 2 It can be seen that after multi-gradient acid leaching, the crack channels are significantly enlarged, increasing the contact between the acid and impurity elements, thus improving the removal efficiency.

[0113] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for removing Ca element from a high-purity quartz sand sample, characterized in that, Includes the following steps: S1, One-time hydrochloric acid leaching The high-purity quartz sample after preliminary purification was placed in a microwave device and subjected to the first microwave acid leaching treatment with hydrochloric acid to obtain leaching sample one. Then, the leached sample 1 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 1; S2, hydrofluoric acid leaching Product 1 was placed in a microwave device and subjected to a second microwave acid leaching treatment with hydrofluoric acid to obtain leaching sample 2. Then, the leached sample 2 was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product 2; S3, secondary hydrochloric acid leaching Product 2 was placed in a microwave device and subjected to a third microwave acid leaching treatment with hydrochloric acid to obtain leaching sample 3. Then, the leached sample three was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain product three; S4, hydrochloric acid and hydrofluoric acid acid leaching Product 3 was placed in a microwave device and subjected to a fourth microwave acid leaching treatment using a mixed acid solution of hydrochloric acid and hydrofluoric acid to obtain leaching sample 4. Then, the leached sample four was repeatedly rinsed with deionized water until the aqueous solution was neutral, filtered, washed and dried to obtain a high-purity quartz product.

2. The method of claim 1, wherein: In step S1, the solid-liquid ratio of the first microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrochloric acid used in the first microwave acid leaching is 5% to 20%.

3. The method of claim 1, wherein: In step S1, the first microwave acid immersion time is 1 to 8 hours, the first microwave acid immersion temperature is 30°C to 100°C, and the microwave power used for the first microwave acid immersion is 100 to 800W.

4. The method of claim 1, wherein: In step S2, the solid-liquid ratio of the second microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrofluoric acid used in the second microwave acid leaching is 5% to 20%.

5. The method of claim 4, wherein: In step S2, the second microwave acid immersion time is 1 to 8 hours, the second microwave acid immersion temperature is 30°C to 100°C, and the microwave power of the second microwave acid immersion is 100 to 800W.

6. The method of claim 1, wherein: In step S3, the solid-liquid ratio of the third microwave acid leaching is 1:2 to 1:6, and the mass fraction of hydrochloric acid used in the third microwave acid leaching is 5% to 20%.

7. The method of claim 1, wherein: In step S3, the third microwave acid immersion time is 1 to 8 hours, the third microwave acid immersion temperature is 30°C to 100°C, and the microwave power used for the third microwave acid immersion is 100 to 800W.

8. The method of claim 1, wherein: In step S4, the solid-liquid ratio of the fourth microwave acid leaching is 1:2 to 1:6, the mass fraction of the mixed acid solution used in the fourth microwave acid leaching is 5% to 20%, and the mass ratio of hydrochloric acid to hydrofluoric acid is 9:1 to 1:

9.

9. The method of claim 1, wherein: In step S4, the fourth microwave acid leaching time is 1 to 8 hours, the fourth microwave acid leaching temperature is 30°C to 100°C, and the microwave power used for the fourth microwave acid leaching is 100 to 800W.

10. A high purity quartz sand, characterized by, The high-purity quartz sand is prepared by the method described in any one of claims 1 to 9, wherein the purity of the high-purity quartz sand is greater than 99.9980%.

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